ISO 5-3:2009
(Main)Photography and graphic technology — Density measurements — Part 3: Spectral conditions
Photography and graphic technology — Density measurements — Part 3: Spectral conditions
ISO 5-3:2009 specifies spectral conditions and computational procedures for the definition of several types of ISO 5 standard densities used in imaging applications in photography and graphic technology.
Photographie et technologie graphique — Mesurages de la densité — Partie 3: Conditions spectrales
Fotografija in grafična tehnologija - Merjenje optične gostote - 3. del: Spektralni pogoji
Ta del ISO 5 določa spektralne pogoje in računske postopke za opredelitev več vrst optičnih gostot po standardu ISO 5, ki se uporabljajo pri slikovnih aplikacijah pri fotografiji in grafični tehnologiji.
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INTERNATIONAL ISO
STANDARD 5-3
Third edition
2009-12-01
Photography and graphic technology —
Density measurements —
Part 3:
Spectral conditions
Photographie et technologie graphique — Mesurages de la densité —
Partie 3: Conditions spectrales
Reference number
ISO 5-3:2009(E)
©
ISO 2009
---------------------- Page: 1 ----------------------
ISO 5-3:2009(E)
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INTERNATIONAL ISO
STANDARD 5-3
Third edition
2009-12-01
Photography and graphic technology —
Density measurements —
Part 3:
Spectral conditions
Photographie et technologie graphique — Mesurages de la densité —
Partie 3: Conditions spectrales
Reference number
ISO 5-3:2009(E)
©
ISO 2009
---------------------- Page: 1 ----------------------
ISO 5-3:2009(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2009
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 5-3:2009(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Requirements.3
4.1 General .3
4.2 Influx spectrum.3
4.3 Types of instruments .5
4.4 Spectral products.5
4.5 Computation of ISO 5 standard density from spectral data .6
4.6 Sample conditions.6
4.7 Reference standards.6
5 Notation .7
6 Types of ISO 5 standard density.7
6.1 ISO 5 standard visual density .7
6.2 ISO 5 standard printing density.7
6.3 ISO 5 standard status A density .8
6.4 ISO 5 standard status M density.9
6.5 ISO 5 standard status T density.9
6.6 ISO 5 standard status E density .9
6.7 ISO 5 standard narrow-band density.10
6.8 ISO 5 standard status I density.10
6.9 ISO 5 standard type 3 density.11
7 Spectral conformance, repeatability, stability and bias.11
7.1 Spectral conformance.11
7.2 Repeatability, stability and bias.11
Annex A (normative) Reference tables of spectral products and weighting factors.25
Annex B (normative) Computation of ISO 5 standard density from spectral data .26
Annex C (informative) Method used to derive spectral weighting factors based on historical
spectral product data.28
Annex D (informative) Method used to derive abridged spectral weighting factors from 1 nm
reference spectral product data.29
Annex E (informative) Plots of relative spectral power distributions for influx spectra, and
spectral products for ISO 5 standard density .33
Annex F (informative) Spectral conformance .40
Bibliography.41
© ISO 2009 – All rights reserved iii
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ISO 5-3:2009(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5-3 was prepared by ISO/TC 42, Photography, and ISO/TC 130, Graphic technology, in a Joint Working
Group.
This third edition cancels and replaces the second edition (ISO 5-3:1995), which has been technically revised.
This technical revision takes into account, in particular, computation of ISO 5 standard density from spectral
data, as well as graphic arts considerations. In the course of this technical revision, all parts of ISO 5 have
been reviewed together, and the terminology, nomenclature and technical requirements have been made
consistent across all parts.
ISO 5 consists of the following parts, under the general title Photography and graphic technology — Density
measurements:
⎯ Part 1: Geometry and functional notation
⎯ Part 2: Geometric conditions for transmittance density
⎯ Part 3: Spectral conditions
⎯ Part 4: Geometric conditions for reflection density
iv © ISO 2009 – All rights reserved
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ISO 5-3:2009(E)
Introduction
0.1 General
The ISO 5 series comprises four International Standards that specify the spatial and spectral conditions for
optical densitometry for use in black-and-white and colour imaging applications, as practised in photographic
and graphic technology applications. The term “ISO 5 standard density” is used within the ISO 5 series to refer
to such specified conditions. The more general term “density” is used in its traditional sense when the basic
optical principles and concepts are being discussed.
To define an ISO 5 standard density value fully, it is necessary to specify both the geometric and spectral
conditions of the measuring system. Geometric conditions are described in ISO 5-2 for transmittance ISO 5
standard density, and in ISO 5-4 for reflection ISO 5 standard density. This part of ISO 5 specifies the spectral
conditions for both transmittance and reflection ISO 5 standard density measurements. For many of these
conditions, the term “status density” is used to identify them.
0.2 Density measurement
In photography, optical density is a measure of the modulation of light or other radiant flux by a given area of
the recording medium. The measurement of density can be of interest for various reasons. It might be
necessary to assess the lightness or darkness of an image, to predict how a film or paper will perform in a
printing operation, or to determine a measure of the amounts of colorants in the image for the purpose of
controlling a colour process. If the visual effect is of interest, the spectral conditions of measurement need to
simulate an appropriate illumination and the spectral sensitivity of the eye. For photographic printing
operations, the spectral power distribution of the source to be used in the printing operation and the spectral
sensitivity of the print material need to be simulated. In evaluating original material for colour separation, the
illuminant, the spectral sensitivity of the separation medium, and the spectral transmittance of the tricolour
separation filters (and other optical components) need to be simulated.
In order to provide measurement data that can be properly interpreted by the various users who need to do
so, the provision of standard specifications for the measurement procedure is necessary. ISO 5 provides that
specification. In this part of ISO 5, a number of spectral conditions are specified, including a definition of the
spectral response for each.
NOTE Spectral response is a function of the spectral sensitivity of the photodetector and the spectral modifications
by any of the optics and filters between the plane of the specimen and the photodetector.
In many applications, it is considered desirable for the spectral response to match the spectral sensitivity of
the intended receiver (eye, photographic paper, etc.) used in the practical applications of the product as
described above. However, in other applications, the spectral response is defined somewhat arbitrarily
(though frequently with some regard to the spectral characteristics of the media being measured) to facilitate
unambiguous communication for issues of process control and thus the spectral product also becomes
arbitrary in those instances.
The various spectral conditions specified in this part of ISO 5 have each been shown to be useful to the
application identified. For example, certain types of density measurements are often made to generate
sensitometric curves which are used to characterize the photographic properties of films and papers.
Densities can also be used to perform a photographic tone-reproduction analysis or to monitor operations like
photoprocessing. In graphic technology, reflection density measurements are used for the control of the ink
film thickness, or, more generally, the amount of colorant per area and the determination of the tone values or
other quantities.
© ISO 2009 – All rights reserved v
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ISO 5-3:2009(E)
In the early years of densitometry, the spectral responses of instruments were specified only in terms of the
colour filters used in the construction. Although it was seldom the case, it was assumed that the spectral
responses of the detector and the source spectral energy distributions, as well as all intervening optical
components, were the same in all instruments. In more recent times, densitometry standards have specified
that the combination of all these components equals a given set of published “documentary” values. If each of
these components is approximated by a mathematical function, then their combination could be approximated
by simply multiplying the spectral characteristics, wavelength by wavelength, and compiling the results into a
table of numbers known as the spectral products. Such a specification allows flexibility to the manufacturer
while providing for improved accuracy and precision. It also allows for reference materials to be manufactured
and certified based on fundamental measurements.
0.3 Calculation of density
In this revision of this part of ISO 5, it has been recognized that the use of simple filter instruments is in
decline. The more common method of “measuring” ISO 5 standard density makes use of computations based
on measurements of the spectral reflectance factor or spectral transmittance of the specimen under study.
Many users have achieved this calculation in the past by summing, over the full wavelength range, the product
of the spectral reflectance factor or transmittance and the spectral products provided in previous editions of
this international standard (defined at 10 nm intervals), after converting them to the linear domain. However,
such a procedure is not strictly accurate. The spectral products are assumed to be the specification, at 10 nm
intervals, of the physical spectral characteristics of a device obtained by combining spectral data pertaining to
its illumination source and its optical components. Where measurements of samples made with a device
conforming to this specification were compared to those computed from spectral data of the same samples,
calculated by summing over the full wavelength range the product of the spectral data and the linear form of
the 10 nm spectral products, small differences would be found. Although such errors are likely to be very small
with the typical samples encountered in photography and graphic technology (probably in the third decimal
place), such a situation is still undesirable.
Thus, for computation purposes, the older, coarsely sampled tables of spectral products have been
supplemented in this revision with the concept of spectral weighting factors. To achieve these, the 10 nm
spectral products defined in this and previous editions of this part of ISO 5 have been interpolated in the log
domain to 1 nm intervals, using the method defined in Annex D, converted to the linear domain, and
normalized to a peak value of 1. Additional sets of spectral weighting factors have then been derived from
these for use with data measured at intervals greater than 1 nm and any densities calculated from these
weighting factors, using the methodology defined in Annex B, will exactly match those obtained with filter
instruments conforming exactly to the 10 nm spectral products. Of course, the values for the 10 nm spectral
weighting factors differ slightly from those for the 10 nm spectral products, when converted to the linear
domain, because the computation of ISO 5 standard density (as opposed to the direct measurement of ISO 5
standard density) is a convolution of spectral weighting factors and spectral reflectance factor (or
transmittance) at discrete intervals over the appropriate wavelength range. Since the spectral weighting
factors include both the densitometric spectral products and the coefficients of a polynomial for interpolating
the spectral reflectance factor or transmittance, the table entry at a given wavelength might occasionally be a
small negative value. This will not result in negative densities for any typical media, nor does it imply negative
spectral products. The sums will always be positive and the logarithms will have the appropriate magnitude for
the spectrally integrated readings.
It is important to note that the relative (normalized to the peak value) values for the spectral products have not
changed. The interpolation to 1 nm intervals in all cases has left the 10 nm values for relative spectral products
unchanged, except for a linear scaling. These data are still considered to be the primary definition of the
spectral products in this part of ISO 5. Therefore, the spectral products that a filter instrument is expected to
match are still the same, but they have now also been defined at finer data intervals. The assumption is made
that at a data interval of 1 nm, the spectral products can also be used as weighting factors for computation
from spectral data recorded at, or interpolated to, that same spectral resolution. However, for practical work,
where the spectral data are usually sampled more coarsely than this, weighting factors have been calculated
from these 1 nm tables. Such an approach is consistent with more recent practice in colorimetry and provides
the “best” approximation to calculations made with finer resolution data. These weighting functions will also
provide data that are consistent with those made with a “filter” instrument conforming to the 10 nm spectral
products defined in this part of ISO 5. Thus it is recommended that the weighting factors, rather than the
spectral products, are to be used when calculating ISO 5 standard density from spectral reflectance factor or
transmittance data collected by practical instruments at 10 nm or 20 nm wavelength intervals.
vi © ISO 2009 – All rights reserved
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ISO 5-3:2009(E)
See Annexes B, C and D for further discussion of spectral weighting factors and how they were calculated for
this revision of this part of ISO 5.
0.4 Sources of illumination
The traditionally specified spectral power distribution of the incident flux for transmittance ISO 5 standard
density measurements differs from that specified for reflection ISO 5 standard density measurements,
although both are based on a Planckian radiation at a temperature of approximately 2 856 K as defined in
ISO 11664-2. This is the spectral distribution known as CIE standard illuminant A, adopted by the CIE in 1931,
and it can be approximated by an incandescent tungsten-filament lamp operated at a distribution temperature
of 2 856 K. The spectral distribution for transmittance density measurements is modified by a heat-absorbing
filter to protect the specimen and optical system from heat. The requirement to provide in densitometers a
spectral power distribution close to that specified is particularly important because many graphic arts
materials, especially print substrates, and some photographic materials contain optical brightening agents
(OBAs) and exhibit significant fluorescence. If fluorescence is not an issue, the spectral power distribution of
the incident flux is less significant and can deviate from that specified, so long as the specified spectral
product is maintained. Furthermore, when fluorescence is not an issue, the same spectral reflectance factor
data can be used for calculating both colorimetric quantities and reflection ISO 5 standard density.
In this edition of ISO 5, the requirement to use CIE standard illuminant A for reflection measurements and the
modified illuminant A for transmittance measurements is maintained for photographic products. However, in
an attempt to maintain compatibility with colorimetric measurements made in accordance with ISO 13655 in
the graphic arts industry, three additional illumination conditions are introduced for graphic arts use. These are
based on the conditions specified in ISO 13655 and are as follows:
⎯ M1: illuminant D50,
⎯ M2: source that only contains substantial radiation power in the wavelength range above 400 nm, and
⎯ M3: addition of a polarization filter to condition 2.
For materials without optical brighteners, these variations in illumination have no effect, but because the level
of OBAs present is often unknown it is important that the illumination condition used be clearly identified.
Some process control density measuring devices are also being introduced that use a light emitting diode
(LED) as the illumination source and meet the requirements of illumination condition M2. Care is advised
when comparing measurements made with differing illumination conditions, particularly when used to compare
process control measurements between colorants with significantly different spectral characteristics.
0.5 Calibration standards
Many older standards for reflection density specified the use of barium sulfate (BaSO ) as the reference
4
standard. However, pressed barium sulfate (BaSO ) is fragile, variable from batch to batch of powder, variable
4
from pressing to pressing, and its reflectance changes appreciably in the first few days after pressing. In 1969,
the CIE recommended that all reflectance factors and, by inference, the corresponding reflection densities be
reported relative to a perfectly reflecting and perfectly diffusing material. This is specified to be the reference
for calibration in ISO 5.
In day-to-day operation, reflection densitometers are usually calibrated with materials from the instrument
manufacturer or with certified reference materials (CRMs) available from a number of sources. These working
standards need to be calibrated with respect to primary standards that are calibrated with respect to the
perfect reflecting diffuser by absolute methods in national standards laboratories.
© ISO 2009 – All rights reserved vii
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INTERNATIONAL STANDARD ISO 5-3:2009(E)
Photography and graphic technology — Density
measurements —
Part 3:
Spectral conditions
1 Scope
This part of ISO 5 specifies spectral conditions and computational procedures for the definition of several
types of ISO 5 standard densities used in imaging applications in photography and graphic technology.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5-1, Photography and graphic technology — Density measurements — Part 1: Geometry and functional
notation
ISO 5-2, Photography and graphic technology — Density measurements — Part 2: Geometric conditions for
transmittance density
ISO 5-4, Photography and graphic technology — Density measurements — Part 4: Geometric conditions for
reflection density
ISO 11664-2, Colorimetry — Part 2: CIE standard illuminants
ISO 14807, Photography — Transmission and reflection densitometers — Method for determining performance
1)
IEC 60050-845:1987 , International Electrotechnical Vocabulary. Lighting
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5-1, IEC 60050-845:1987⏐CIE 17.4:1987
and the following apply.
3.1
CIE standard illuminant A
Planckian radiation at a temperature of approximately 2 856 K, as defined in ISO 11664-2
NOTE 1 The radiation of a gas-filled coil tungsten filament lamp operated at a colour temperature of 2 856 K will
approximate this spectral distribution, and thus can serve as a practical realization of this standard illuminant.
1) IEC 60050-845:1987 is a joint publication with the International Commission on Illumination (CIE). It is identical to
CIE 17.4:1987, International Lighting Vocabulary.
© ISO 2009 – All rights reserved 1
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ISO 5-3:2009(E)
NOTE 2 It is important to note the distinction between an illuminant and a source. An illuminant is defined by a table of
relative spectral power distribution that might not be precisely realized in practice. A source is an object that produces
radiant flux.
3.2
efflux spectrum
spectral power distribution of the radiant flux collected by the receiver from the reference plane
NOTE This is a function of the influx spectrum and the spectral reflectance or transmittance characteristics of the
standard or specimen.
3.3
influx spectrum
S
spectral distribution of the radiometric quantity, such as radiance, irradiance or radiant flux, incident upon the
sampling aperture
NOTE This is a function of the source and optics used for the illumination.
[ISO 5-1:2009, definition 3.11]
3.4
ISO 5 standard density
density value obtained using an instrument conforming to one of the geometries specified in ISO 5-2 or
ISO 5-4, and one of the spectral definitions in ISO 5-3
[ISO 5-1:2009, definition 3.12]
3.5
peak wavelength
wavelength at which the spectral product or weighting factor is a maximum
3.6
receiver
portion of the densitometer that senses the efflux, including the collection optics and detector
[ISO 5-4:2009, definition 3.3]
3.7
sideband rejection
degree to which radiant flux outside a desired spectral bandwidth is blocked or suppressed
NOTE It is usually expressed as the ratio of the integrated energy within the desired bandwidth to the integrated
radiant flux outside the bandwidth.
3.8
source
object that produces radiant flux
3.9
spectral bandwidth
wavelength interval between which the spectral product has decreased to a designated percentage of its
maximum
3.10
spectral product
Π
product of the influx spectrum and the spectral responsivity
2 © ISO 2009 – All rights reserved
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ISO 5-3:2009(E)
3.11
spectral reflectance factor
ratio of the reflected flux to the absolute reference reflected flux under the same geometrical and spectral
conditions of measurement, as a function of wavelength
NOTE Adapted from ASTM E284.
3.12
spectral responsivity
s
output signal of a receiver per unit input of radiant flux as a function of wavelength
NOTE Adapted from ASTM E284.
[ISO 5-1:2009, definition 3.20]
3.13
spectral transmittance
ratio of the transmitted flux to the incident flux under specified geometrical and spectral conditions of
measurement
3.14
spectral weighting factor
factor obtained from the spectral product, tabulated at specified wavelength intervals
NOTE To compute density values from spectral weighting factors, see Annex B.
4 Requirements
4.1 General
ISO 5 standard density is the logarithm to the base 10 of the ratio (see Annex B) of the integration of the
spectral products and either spectral reflectance factor or spectral transmittance of the material under
examination, and the integration of the spectral products alone. The spectral conditions for the various types
of ISO 5 standard density specified in this part of ISO 5 are given by the various spectral products, defined at
10 nm intervals, specified in this, and previous editions, of this part of ISO 5. However, these have been
extended to provide greater precision by means of tabulated values spaced at 1 nm intervals and normalized
to a value of 1 at the peak wavelength. These data are directly equivalent to the 10 nm data, although defined
in the linear domain. In addition, abridged weighting factors are provided for convenience in determining ISO 5
standard density using instruments where spectral reflectance factor or transmittance data are available at
intervals of 10 nm or 20 nm. Further information pertaining to these weighting factors, and their derivation, is
given in the Introduction and in Annexes B, C and D.
4.2 Influx spectrum
4.2.1 General
To unambiguously define the determination of ISO 5 standard density in the presence of materials which may
fluoresce, it is necessary to also specify the spectral characteristics of the influx spectrum, S, as well as the
spectral products.
The historic radiation source for densitometry has been an incandescent lamp with a relative spectral power
distribution
...
SLOVENSKI STANDARD
SIST ISO 5-3:2010
01-maj-2010
1DGRPHãþD
SIST ISO 5-3:1996
)RWRJUDILMDLQJUDILþQDWHKQRORJLMD0HUMHQMHRSWLþQHJRVWRWHGHO 6SHNWUDOQL
SRJRML
Photography and graphic technology - Density measurements - Part 3: Spectral
conditions
Photographie et technologie graphique - Mesurages de la densité - Partie 3: Conditions
spectrales
Ta slovenski standard je istoveten z: ISO 5-3:2009
ICS:
37.040.01 Fotografija na splošno Photography in general
SIST ISO 5-3:2010 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST ISO 5-3:2010
---------------------- Page: 2 ----------------------
SIST ISO 5-3:2010
INTERNATIONAL ISO
STANDARD 5-3
Third edition
2009-12-01
Photography and graphic technology —
Density measurements —
Part 3:
Spectral conditions
Photographie et technologie graphique — Mesurages de la densité —
Partie 3: Conditions spectrales
Reference number
ISO 5-3:2009(E)
©
ISO 2009
---------------------- Page: 3 ----------------------
SIST ISO 5-3:2010
ISO 5-3:2009(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2009
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 5-3:2010
ISO 5-3:2009(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Requirements.3
4.1 General .3
4.2 Influx spectrum.3
4.3 Types of instruments .5
4.4 Spectral products.5
4.5 Computation of ISO 5 standard density from spectral data .6
4.6 Sample conditions.6
4.7 Reference standards.6
5 Notation .7
6 Types of ISO 5 standard density.7
6.1 ISO 5 standard visual density .7
6.2 ISO 5 standard printing density.7
6.3 ISO 5 standard status A density .8
6.4 ISO 5 standard status M density.9
6.5 ISO 5 standard status T density.9
6.6 ISO 5 standard status E density .9
6.7 ISO 5 standard narrow-band density.10
6.8 ISO 5 standard status I density.10
6.9 ISO 5 standard type 3 density.11
7 Spectral conformance, repeatability, stability and bias.11
7.1 Spectral conformance.11
7.2 Repeatability, stability and bias.11
Annex A (normative) Reference tables of spectral products and weighting factors.25
Annex B (normative) Computation of ISO 5 standard density from spectral data .26
Annex C (informative) Method used to derive spectral weighting factors based on historical
spectral product data.28
Annex D (informative) Method used to derive abridged spectral weighting factors from 1 nm
reference spectral product data.29
Annex E (informative) Plots of relative spectral power distributions for influx spectra, and
spectral products for ISO 5 standard density .33
Annex F (informative) Spectral conformance .40
Bibliography.41
© ISO 2009 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 5-3:2010
ISO 5-3:2009(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5-3 was prepared by ISO/TC 42, Photography, and ISO/TC 130, Graphic technology, in a Joint Working
Group.
This third edition cancels and replaces the second edition (ISO 5-3:1995), which has been technically revised.
This technical revision takes into account, in particular, computation of ISO 5 standard density from spectral
data, as well as graphic arts considerations. In the course of this technical revision, all parts of ISO 5 have
been reviewed together, and the terminology, nomenclature and technical requirements have been made
consistent across all parts.
ISO 5 consists of the following parts, under the general title Photography and graphic technology — Density
measurements:
⎯ Part 1: Geometry and functional notation
⎯ Part 2: Geometric conditions for transmittance density
⎯ Part 3: Spectral conditions
⎯ Part 4: Geometric conditions for reflection density
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Introduction
0.1 General
The ISO 5 series comprises four International Standards that specify the spatial and spectral conditions for
optical densitometry for use in black-and-white and colour imaging applications, as practised in photographic
and graphic technology applications. The term “ISO 5 standard density” is used within the ISO 5 series to refer
to such specified conditions. The more general term “density” is used in its traditional sense when the basic
optical principles and concepts are being discussed.
To define an ISO 5 standard density value fully, it is necessary to specify both the geometric and spectral
conditions of the measuring system. Geometric conditions are described in ISO 5-2 for transmittance ISO 5
standard density, and in ISO 5-4 for reflection ISO 5 standard density. This part of ISO 5 specifies the spectral
conditions for both transmittance and reflection ISO 5 standard density measurements. For many of these
conditions, the term “status density” is used to identify them.
0.2 Density measurement
In photography, optical density is a measure of the modulation of light or other radiant flux by a given area of
the recording medium. The measurement of density can be of interest for various reasons. It might be
necessary to assess the lightness or darkness of an image, to predict how a film or paper will perform in a
printing operation, or to determine a measure of the amounts of colorants in the image for the purpose of
controlling a colour process. If the visual effect is of interest, the spectral conditions of measurement need to
simulate an appropriate illumination and the spectral sensitivity of the eye. For photographic printing
operations, the spectral power distribution of the source to be used in the printing operation and the spectral
sensitivity of the print material need to be simulated. In evaluating original material for colour separation, the
illuminant, the spectral sensitivity of the separation medium, and the spectral transmittance of the tricolour
separation filters (and other optical components) need to be simulated.
In order to provide measurement data that can be properly interpreted by the various users who need to do
so, the provision of standard specifications for the measurement procedure is necessary. ISO 5 provides that
specification. In this part of ISO 5, a number of spectral conditions are specified, including a definition of the
spectral response for each.
NOTE Spectral response is a function of the spectral sensitivity of the photodetector and the spectral modifications
by any of the optics and filters between the plane of the specimen and the photodetector.
In many applications, it is considered desirable for the spectral response to match the spectral sensitivity of
the intended receiver (eye, photographic paper, etc.) used in the practical applications of the product as
described above. However, in other applications, the spectral response is defined somewhat arbitrarily
(though frequently with some regard to the spectral characteristics of the media being measured) to facilitate
unambiguous communication for issues of process control and thus the spectral product also becomes
arbitrary in those instances.
The various spectral conditions specified in this part of ISO 5 have each been shown to be useful to the
application identified. For example, certain types of density measurements are often made to generate
sensitometric curves which are used to characterize the photographic properties of films and papers.
Densities can also be used to perform a photographic tone-reproduction analysis or to monitor operations like
photoprocessing. In graphic technology, reflection density measurements are used for the control of the ink
film thickness, or, more generally, the amount of colorant per area and the determination of the tone values or
other quantities.
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In the early years of densitometry, the spectral responses of instruments were specified only in terms of the
colour filters used in the construction. Although it was seldom the case, it was assumed that the spectral
responses of the detector and the source spectral energy distributions, as well as all intervening optical
components, were the same in all instruments. In more recent times, densitometry standards have specified
that the combination of all these components equals a given set of published “documentary” values. If each of
these components is approximated by a mathematical function, then their combination could be approximated
by simply multiplying the spectral characteristics, wavelength by wavelength, and compiling the results into a
table of numbers known as the spectral products. Such a specification allows flexibility to the manufacturer
while providing for improved accuracy and precision. It also allows for reference materials to be manufactured
and certified based on fundamental measurements.
0.3 Calculation of density
In this revision of this part of ISO 5, it has been recognized that the use of simple filter instruments is in
decline. The more common method of “measuring” ISO 5 standard density makes use of computations based
on measurements of the spectral reflectance factor or spectral transmittance of the specimen under study.
Many users have achieved this calculation in the past by summing, over the full wavelength range, the product
of the spectral reflectance factor or transmittance and the spectral products provided in previous editions of
this international standard (defined at 10 nm intervals), after converting them to the linear domain. However,
such a procedure is not strictly accurate. The spectral products are assumed to be the specification, at 10 nm
intervals, of the physical spectral characteristics of a device obtained by combining spectral data pertaining to
its illumination source and its optical components. Where measurements of samples made with a device
conforming to this specification were compared to those computed from spectral data of the same samples,
calculated by summing over the full wavelength range the product of the spectral data and the linear form of
the 10 nm spectral products, small differences would be found. Although such errors are likely to be very small
with the typical samples encountered in photography and graphic technology (probably in the third decimal
place), such a situation is still undesirable.
Thus, for computation purposes, the older, coarsely sampled tables of spectral products have been
supplemented in this revision with the concept of spectral weighting factors. To achieve these, the 10 nm
spectral products defined in this and previous editions of this part of ISO 5 have been interpolated in the log
domain to 1 nm intervals, using the method defined in Annex D, converted to the linear domain, and
normalized to a peak value of 1. Additional sets of spectral weighting factors have then been derived from
these for use with data measured at intervals greater than 1 nm and any densities calculated from these
weighting factors, using the methodology defined in Annex B, will exactly match those obtained with filter
instruments conforming exactly to the 10 nm spectral products. Of course, the values for the 10 nm spectral
weighting factors differ slightly from those for the 10 nm spectral products, when converted to the linear
domain, because the computation of ISO 5 standard density (as opposed to the direct measurement of ISO 5
standard density) is a convolution of spectral weighting factors and spectral reflectance factor (or
transmittance) at discrete intervals over the appropriate wavelength range. Since the spectral weighting
factors include both the densitometric spectral products and the coefficients of a polynomial for interpolating
the spectral reflectance factor or transmittance, the table entry at a given wavelength might occasionally be a
small negative value. This will not result in negative densities for any typical media, nor does it imply negative
spectral products. The sums will always be positive and the logarithms will have the appropriate magnitude for
the spectrally integrated readings.
It is important to note that the relative (normalized to the peak value) values for the spectral products have not
changed. The interpolation to 1 nm intervals in all cases has left the 10 nm values for relative spectral products
unchanged, except for a linear scaling. These data are still considered to be the primary definition of the
spectral products in this part of ISO 5. Therefore, the spectral products that a filter instrument is expected to
match are still the same, but they have now also been defined at finer data intervals. The assumption is made
that at a data interval of 1 nm, the spectral products can also be used as weighting factors for computation
from spectral data recorded at, or interpolated to, that same spectral resolution. However, for practical work,
where the spectral data are usually sampled more coarsely than this, weighting factors have been calculated
from these 1 nm tables. Such an approach is consistent with more recent practice in colorimetry and provides
the “best” approximation to calculations made with finer resolution data. These weighting functions will also
provide data that are consistent with those made with a “filter” instrument conforming to the 10 nm spectral
products defined in this part of ISO 5. Thus it is recommended that the weighting factors, rather than the
spectral products, are to be used when calculating ISO 5 standard density from spectral reflectance factor or
transmittance data collected by practical instruments at 10 nm or 20 nm wavelength intervals.
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See Annexes B, C and D for further discussion of spectral weighting factors and how they were calculated for
this revision of this part of ISO 5.
0.4 Sources of illumination
The traditionally specified spectral power distribution of the incident flux for transmittance ISO 5 standard
density measurements differs from that specified for reflection ISO 5 standard density measurements,
although both are based on a Planckian radiation at a temperature of approximately 2 856 K as defined in
ISO 11664-2. This is the spectral distribution known as CIE standard illuminant A, adopted by the CIE in 1931,
and it can be approximated by an incandescent tungsten-filament lamp operated at a distribution temperature
of 2 856 K. The spectral distribution for transmittance density measurements is modified by a heat-absorbing
filter to protect the specimen and optical system from heat. The requirement to provide in densitometers a
spectral power distribution close to that specified is particularly important because many graphic arts
materials, especially print substrates, and some photographic materials contain optical brightening agents
(OBAs) and exhibit significant fluorescence. If fluorescence is not an issue, the spectral power distribution of
the incident flux is less significant and can deviate from that specified, so long as the specified spectral
product is maintained. Furthermore, when fluorescence is not an issue, the same spectral reflectance factor
data can be used for calculating both colorimetric quantities and reflection ISO 5 standard density.
In this edition of ISO 5, the requirement to use CIE standard illuminant A for reflection measurements and the
modified illuminant A for transmittance measurements is maintained for photographic products. However, in
an attempt to maintain compatibility with colorimetric measurements made in accordance with ISO 13655 in
the graphic arts industry, three additional illumination conditions are introduced for graphic arts use. These are
based on the conditions specified in ISO 13655 and are as follows:
⎯ M1: illuminant D50,
⎯ M2: source that only contains substantial radiation power in the wavelength range above 400 nm, and
⎯ M3: addition of a polarization filter to condition 2.
For materials without optical brighteners, these variations in illumination have no effect, but because the level
of OBAs present is often unknown it is important that the illumination condition used be clearly identified.
Some process control density measuring devices are also being introduced that use a light emitting diode
(LED) as the illumination source and meet the requirements of illumination condition M2. Care is advised
when comparing measurements made with differing illumination conditions, particularly when used to compare
process control measurements between colorants with significantly different spectral characteristics.
0.5 Calibration standards
Many older standards for reflection density specified the use of barium sulfate (BaSO ) as the reference
4
standard. However, pressed barium sulfate (BaSO ) is fragile, variable from batch to batch of powder, variable
4
from pressing to pressing, and its reflectance changes appreciably in the first few days after pressing. In 1969,
the CIE recommended that all reflectance factors and, by inference, the corresponding reflection densities be
reported relative to a perfectly reflecting and perfectly diffusing material. This is specified to be the reference
for calibration in ISO 5.
In day-to-day operation, reflection densitometers are usually calibrated with materials from the instrument
manufacturer or with certified reference materials (CRMs) available from a number of sources. These working
standards need to be calibrated with respect to primary standards that are calibrated with respect to the
perfect reflecting diffuser by absolute methods in national standards laboratories.
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INTERNATIONAL STANDARD ISO 5-3:2009(E)
Photography and graphic technology — Density
measurements —
Part 3:
Spectral conditions
1 Scope
This part of ISO 5 specifies spectral conditions and computational procedures for the definition of several
types of ISO 5 standard densities used in imaging applications in photography and graphic technology.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5-1, Photography and graphic technology — Density measurements — Part 1: Geometry and functional
notation
ISO 5-2, Photography and graphic technology — Density measurements — Part 2: Geometric conditions for
transmittance density
ISO 5-4, Photography and graphic technology — Density measurements — Part 4: Geometric conditions for
reflection density
ISO 11664-2, Colorimetry — Part 2: CIE standard illuminants
ISO 14807, Photography — Transmission and reflection densitometers — Method for determining performance
1)
IEC 60050-845:1987 , International Electrotechnical Vocabulary. Lighting
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5-1, IEC 60050-845:1987⏐CIE 17.4:1987
and the following apply.
3.1
CIE standard illuminant A
Planckian radiation at a temperature of approximately 2 856 K, as defined in ISO 11664-2
NOTE 1 The radiation of a gas-filled coil tungsten filament lamp operated at a colour temperature of 2 856 K will
approximate this spectral distribution, and thus can serve as a practical realization of this standard illuminant.
1) IEC 60050-845:1987 is a joint publication with the International Commission on Illumination (CIE). It is identical to
CIE 17.4:1987, International Lighting Vocabulary.
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NOTE 2 It is important to note the distinction between an illuminant and a source. An illuminant is defined by a table of
relative spectral power distribution that might not be precisely realized in practice. A source is an object that produces
radiant flux.
3.2
efflux spectrum
spectral power distribution of the radiant flux collected by the receiver from the reference plane
NOTE This is a function of the influx spectrum and the spectral reflectance or transmittance characteristics of the
standard or specimen.
3.3
influx spectrum
S
spectral distribution of the radiometric quantity, such as radiance, irradiance or radiant flux, incident upon the
sampling aperture
NOTE This is a function of the source and optics used for the illumination.
[ISO 5-1:2009, definition 3.11]
3.4
ISO 5 standard density
density value obtained using an instrument conforming to one of the geometries specified in ISO 5-2 or
ISO 5-4, and one of the spectral definitions in ISO 5-3
[ISO 5-1:2009, definition 3.12]
3.5
peak wavelength
wavelength at which the spectral product or weighting factor is a maximum
3.6
receiver
portion of the densitometer that senses the efflux, including the collection optics and detector
[ISO 5-4:2009, definition 3.3]
3.7
sideband rejection
degree to which radiant flux outside a desired spectral bandwidth is blocked or suppressed
NOTE It is usually expressed as the ratio of the integrated energy within the desired bandwidth to the integrated
radiant flux outside the bandwidth.
3.8
source
object that produces radiant flux
3.9
spectral bandwidth
wavelength interval between which the spectral product has decreased to a designated percentage of its
maximum
3.10
spectral product
Π
product of the influx spectrum and the spectral responsivity
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3.11
spectral reflectance factor
ratio of the reflected flux to the absolute reference reflected flux under the same geometrical and spectral
conditions of measurement, as a function of wavelength
NOTE Adapted from ASTM E284.
3.12
spectral responsivity
s
output signal of a receiver per unit input of radiant flux as a function of wavelength
NOTE Adapted from ASTM E284.
[ISO 5-1:2009, definition 3.20]
3.13
spectral transmittance
ratio of the transmitted flux to the incident flux under specified geometrical and spectral conditions of
measurement
3.14
spectral weighting factor
factor obtained from the spectral product, tabulated at specified wavelength intervals
NOTE To compute density values from spectral weighting factors, see Annex B.
4 Requirements
4.1 General
ISO 5 standard density is the logarithm to the base 10 of the ratio (see Annex B) of the integration of the
spectral products and either spectral reflectance factor or spectral transmittance of the material under
examination, and the integration of the spectral products alone. The spectral conditions for the various types
of ISO 5 standard density specified in this part of ISO 5 are given by the various spectral products, defined at
10 nm intervals, specified in this, and previous editions, of this part of ISO 5. However, these have
...
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